A good method of discovery is to imagine certain members of a system removed and then see how what is left would behave: for example, where would we be if iron were absent from the world: this is an old example.

The Greeks possessed a knowledge of human nature we seem hardly able to attain to without passing through the strengthening hibernation of a new barbarism.

Everyone is a genius at least once a year.

Be attentive, feel nothing in vain, measure and compare: this is the whole law of philosophy.

Perhaps in time the so-called Dark Ages will be thought of as including our own.

When a book and a head collide and a hollow sound is heard, must it always have come from the book?

It is too bad if you have to do everything upon reflection and can't do anything from early habit.